Compressed gas electrical circuit breaker

ABSTRACT

A compressed-gas electrical breaker, is disclosed in the switching chamber of which are arranged a compression space, a fixed contact, a movable contact and a blasting device connected with the movable contact. A movable nozzle body, designed as a blast piston is connected with the movable contact, and operates in conjunction with a spring-loaded shield. The spring-loaded shield is movably guided on the stationary contact and is adapted to be displaced by the nozzle body from the open position of the breaker in which the shield covers the stationary contact to the closed position of the breaker in which the shield engages the nozzle member to seal the compression space of the breaker.

United States Patent- [1'91 Slamecka et a1,

COMPRESSED GAS ELECTRICAL CIRCUIT BREAKER lnventors: Ernst Slamecka; Karl Martschini;

Eckhard Pflaum; Heinz-Helmut Schramm, all of Berlin, Germany Siemens Aktiengesellschaft, Munich, Germany Filed: Aug. 4, 1972 Appl. No.: 277,978

Assignee:

Foreign Application Priority Data Aug. 6, 1971 Germany 2140284 US. Cl. 200/148 A, 200/150 G Int. Cl. H01h 33/70 Field of Search 200/148 A, 150 G v References Cited UNITED STATES PATENTS 5/1951 Thibaudat zoo/14s A 4/1960 Baker 200/148 A 10/1965 Cromer 200/148 B [451 July 16, 1974 3,527,912 9/1970 Jaillet 200/150 G 3,659,065 4/1972 Roidt et a1. ZOO/148 A Primary EXaminen-Robert S. Macon Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin 57 ABSTRACT the shield covers the stationary contact to the closed position of the breaker in which the shield engages the nozzle member to seal the compression space of the breaker.

' 11 Claims, 1 Drawing Figure aw ...E n

PAIENIED JUL 1 man OQl||IlI|| DO All!!! liltin ll u'lll'lllllll' 1 COMPRESSED GAS ELECTRICAL CIRCUIT BREAKER BACKGROUND OF THE INVENTION moved about a fixed piston. Starting with the closed po-.

sition of the contacts, in which the fixed contact penetrates for a substantial part of its length into the nozzle opening of the blast cylinder, the contacts are closed at the rim area of the nozzle body, thereby forming a seal.

In the open position of the breaker, it is particularly advantageous that the shield covers a contact area intended for engagement with the movable contact. This contact is therefore removed from the influence of the switching are.

A compressed-gas electrical circuit breaker according to the invention having a fixed contact, made hollow for the removal of switching gases, affords an advantage if the nozzle of the nozzle body has at its narrowest point a length which is about 0.5 to 1 times the diameter of the stationary contact. The diameter of the stationary contact agrees with the diameter of the nozzle except for the clearance necessary for the movement of the nozzle body. The relatively long length of the beginning of the opening motion. This results in pre-compression of the gas enclosed in the blast cylinder, so that the opening arc generated during the subsequent separation of the contacts is immediately blasted by the precompressed gas and is therefore extinguished rapidly. The space inside the switching chamber, required for the pre-compression of the gas, should be as large as possible to assure the predetermined pre compression pressure.,lts size is also determined by the effective cross sectional area of the blast cylinder, and the stroke of the blast cylinder during its travel up to the point where the contacts separate. On the other hand, to save material, the smallest possible dimensions are desired for the switching chamber included within the switching vessel.

SUMMARY OF THE INVENTION The invention is directed toward improved space utilization in the design of the switching vessel for a compressed-gas electrical circuit breaker, utilizing a movable contact and a blasting device connected thereto.

According to the invention, a nozzle body, which is designed in a known manner as a blast piston-is connected with the movable contact, and a spring-loaded shield is provided. The spring-loaded shield is movably guided at the stationary contact and can be displaced by the nozzle body from its open position against the force of its spring. In the closed position the space available for the nozzle body to attain the precompression of the gas also accommodates the shield for equalizing the electrical field in the gap between the contacts. The shield onlyenters this space when it is to be utilized to effectively influence the field. Shields which equalize the electric field in the gap are known, but require relatively large spaces in the known circuit breakers, such as shown in the published German Patent Application 1,055,643.

The spring-loaded shield in the compressed-gas circuit breaker according to this invention offers the possibility of a better seal of the nozzle body against the stationary contact, so that the effect of the precompression is enhanced. Through the force of the sprthe nozzle makes possible an intensive blast on the breaking are from the separation of the contacts until the lifting of the nozzle from the stationary contact.

The duration of the blast during the time of this motion is proportional to the length of the nozzle. During the time of this motion the switching gases are removed through the hollow stationary contact, which is designed as a discharge tube. The discharge of the switching gases can be promoted if the movable contact is also made hollow as a discharge tube for the switching gases.

With a weak blast, in a gas stream which is led axially toward the arc and continues axially from there, voids can develop. These can be displaced from the critical region of the gap by an axial flow component on the gas into the nozzle is, in a preferred embodiment, between.

20 and 50, relative to the axis'of the nozzle body.

ing acting on the shield, the shield follows the nozzle body, and therefore rests with its free end face against In the compressed-gas circuit breaker according to the invention, the nozzle body encloses the stationary contact, which penetrates through the nozzle. This, together with the shield, which, in the closed position, advantageously rests under spring action against the nozzle body, forms a seal appropriate for the blasting device during the opening motion until the nozzle body is lifted fromthe shield. This also forms an effective seal in the space surrounding the shield. In order to prevent detrimental underpressure in this space, it is connected in the closed breaker position with the interior of the stationary contact by an opening by which undesired pressure differences are thereby equalized.

The utilization of the space occupied by the switching vessel of a compressed-gas electrical circuit breaker according to the invention can be improved if, as is provided in an advantageous embodiment, the switching vessel serves, at least in part, as the blast piston cylinder.

For an improved electrical field in the gap between the contacts, the nozzle body can be provided with an electrically conducting insert.

The utilization of the space occupied by the switching vessel can be further improved thorugh enlarging the usable compression space. In a compressed-gas electrical circuit breaker according to the invention with several spring-loaded laminations arranged at the movable contact for conducting the current and a tube surrounding these laminations, the tube is therefore designed as the support for the blast piston. This results 3 l in a shortening of the canals and in a reduction ofthe axial length of the nozzle body. I

BRIEF DESCRIPTION OF THE DRAWING Further advantages and details of the compressed-gas electrical circuit breaker according to the invention will be described by means of an example of an embodiment with the aid of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The figure shows a schematic, simplified crosssection presentation of the quenching system for a high-voltage, power circuit breaker. To the right of the center line the closed position is illustrated while the left of the center line illustrates the open position. For the sake of simplification, the metal housing belonging to the circuit breaker, which contains sulfur hexafluoride (SP used as the quenching medium at a pressure for example of 8 atm, as well as the drive for the movable contact and the nozzle body, which serves as the blast piston, is not shown. The same quenching system can also be used for open-air circuit breakers of conventional design; The attachment of the quenching system to the bushing of the circuit breaker, which is further required in this case, is not shown in the drawing.

The high-voltage power circuit breaker designed as an electrical, compressed-gas, circuit breaker has a switching vessel 1, which by a support 2 accommodates a stationary contact 3, a movable contact 4and a blast piston 5 connected therewith. The blast piston 5 is designed as a nozzle body and contains a nozzle fitting 6 on the outside diameter of the stationary contact 3.

7 At stationary contact 3, a shield 7, loaded by a spring 8, is movably guided. The shield 7. can be displaced from its open position against the force of the spring '8 by the nozzle body 5. In the open position, the shield 7 covers up a contact area 9 which is intended to engage the movable contact 4. In the closed position the free end face of the shield 7 touches the rim area of the conduction canals are uniformly distributed over the nozzle 6 and thereby effectively seals the compression space .10..

In the example of the embodimentshown, the switching vessel 1 serves at least partially as the cylinder for the blast piston 5. The compression space 10, which is provided for generating a gas flow, is essentially bounded by the switching vessel 1, the movable contact 4 and a contact guide 11. The movable contact 4 as well as the stationary contact 3 are made hollow for the removal of switching gases. The nozzle 6, which surrounds the stationary contact 3 in the closed position, has a length which corresponds approximately to the diameter of the movable contact. This results in a more intensive blast on the interrupt arc, up to the time of the lifting of the nozzle from the stationary contact 3. Up to the time of the lifting of the nozzle body 5 from the stationary contact 3, the shield 7 follows the nozzle body 5 under spring load. The shield 7 serves for the equalization of the electric field in the gap. It consists of insulating material and can be provided on its inside 12 with an electrically conducting coating.

The nozzle body 5 contains canals 13 which lead the quenching gas, particularly SP from the space 10 at an circumference of the tube 18.

During the switching-off motion, in order to prevent a pressure difference impeding the axial flow in the space 14 containing the shield 7, the carrier 2 is provided with an opening 15, which connects the space 14 with the interior of the stationary contact 3.

For equalizing the electric field in the gap, the nozzle body 5 may be provided with an electrically conducting insert 16. At the end face pointing toward the stationary contact 3 the nozzle body 5 is of concave-shape, and with this end face, forms a shield which covers the walls of the blast piston cylinder and preferably acts as a dust and are protector. The concavely shaped end face of the nozzle body 5 corresponds to the shape of the exterior surface of the shield 7, so that toward the end of the opening motion, a ring canal is formed which has a favorable effect on the gas flow.

In the example of the embodiment shown, springloaded laminations 17 enclosed by a tube 18 are arranged at the movable contact 4 for the conduction of the current. For enlarging the effective compression space 10, the tube 18 can be utilized as the support for the blast piston 5.

In the compressed-gas circuit breaker according to the invention, the space required for pre-compression is kept low because of the displaceable shield which only forms an electrode of large area when required, i.e., in the open position. This thereby improves the field configuration in the gap. At the same time the effect of the pre-compression of the gas is enhanced by the seal obtained through the interaction of the nozzle body with the shield.

In the foregoing, the invention has been described in reference to specific exemplary embodiments. It will be evident, however, that variations and modifications, as well as the substitution of equivalent constructions and arrangements for those shown for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawing are accordingly to be regarded in an illustrative rather than in a restrictive sense.

What is claimed is:

1. A compressed-gas electrical circuit breaker comprising: a switching vessel having a compression space; a stationary contact including a contact area; a movable contact movable between closed and open posiangle of preferably 30, relative to the axis of the nozzle body. This causes an axial flow component. The gas tions for slidably engaging said stationary contact at said contact area and for disengaging said contacts respectively; a blasting device within said vessel including a nozzle member'configured as a piston and connected to said movable contact so as to be movable therewith for compressing the gas in said space when the movable contact is moved into said open position, said nozzle member being configured for directing the compressed gas at the are drawn across said contacts as the same disengage; and a spring-loaded shield mounted on said stationary contact in surrounding relation thereto so as to be displaceable against the force of the spring between a first position whereat said sheild closely surrounds said contact area and a second position away from said contact area, said sheild being adapted to be engaged by said nozzle member so as to simultaneously seal the compression space and displace said shield against the force of the spring from said first position to said second position when the breaker is closed, said shield being further adapted to follow said nozzle member and return to said first position under the force of said spring when the breaker is opened so as to closely cover said contact area as said movable contact disengages from said stationary contact whereby said contact area is protected from the action of the arc.

2. A compressed-gas electrical circuit breaker as in claim 1 wherein the stationary Contact is hollow to permit the removal of switching gases.

3. A compressed-gas electrical circuit breaker as in claim 2 in which the nozzle member has a length which is approximately 0.5 to 1 times the diameter of the stationary contact.

4. A compressed-gas electrical circuit breaker as in claim 1 in which the movable contact is hollow to permit the removal of the switching gases.

5. A compressed-gas electrical circuit breaker as in claim 1 in which the nozzle member has canals to feed the quenching gas to the nozzle at a flow angle that causes an axial flow component in the gas.

6. A compressed-gas electrical circuit breaker as in claim 5 in which the angle of the canals in the area v7. A compressed-gas electrical circuit breaker as in claim 1 in which the space in the switching vessel surrounding the shield in the closed position is connected by an opening with the interior of the stationary contact to equalize undesired pressure differences.

' 8. A compressed-gas electrical circuit breaker as in claim 1 in which a portion of thev blast piston cylinder is formed from the switching vessel.

9. A compressed-gas electrical circuit breaker as in claim 1 in which the nozzle member has an electrically conducting insert within the nozzle member.

10. A compressed-gas electrical circuit breaker as in claim 9 further comprising several spring-loaded laminations within a tube disposed around the movable contact and supporting the blast piston.

11. A compressed-gas electrical circuit breaker as in claim 10 in which the nozzle member is of concave shape at its end facing the stationary contact. 

1. A compressed-gas electrical circuit breaker comprising: a switching vessel having a compression space; a stationary contact including a contact area; a movable contact movable between closed and open positions for slidably engaging said stationary contact at said contact area and for disengaging said contacts respectively; a blasting device within said vessel including a nozzle member configured as a piston and connected to said movable contact so as to be movable therewith for compressing the gas in said space when the movable contact is moved into said open position, said nozzle member being configured for directing the compressed gas at the arc drawn across said contacts as the same disengage; and a spring-loaded shield mounted on said stationary contact in surrounding relation thereto so as to be displaceable against the force of the spring between a first position whereat said sheild closely surrounds said contact area and a second position away from said contact area, said sheild being adapted to be engaged by said nozzle member so as to simultaneously seal the compression space and displace said shield against the force of the spring from said first position to said second position when the breaker is closed, said shield being further adapted to follow said nozzle member and return to said first position under the force of said spring when the breaker is opened so as to closely cover said contact area as said movable contact disengages from said stationary contact whereby said contact area is protected from the action of the arc.
 2. A compressed-gas electrical circuit breaker as in claim 1 wherein the stationary contact is hollow to permit the removal of switching gases.
 3. A compressed-gas electrical circuit breaker as in claim 2 in which the nozzle member has a length which is approximately 0.5 to 1 times the diameter of the stationary contact.
 4. A compressed-gas electrical circuit breaker as in claim 1 in which the movable contact is hollow to permit the removal of the switching gases.
 5. A compressed-gas electrical circuit breaker as in claim 1 in which the nozzle member has canals to feed the quenching gas to the nozzle at a flow angle that causes an axial flow component in the gas.
 6. A compressed-gas electrical circuit breaker as in claim 5 in which the angle of the canals in the area where the canals open into the nozzle is between 20* and 50* with respect to the axis of tHe nozzle member.
 7. A compressed-gas electrical circuit breaker as in claim 1 in which the space in the switching vessel surrounding the shield in the closed position is connected by an opening with the interior of the stationary contact to equalize undesired pressure differences.
 8. A compressed-gas electrical circuit breaker as in claim 1 in which a portion of the blast piston cylinder is formed from the switching vessel.
 9. A compressed-gas electrical circuit breaker as in claim 1 in which the nozzle member has an electrically conducting insert within the nozzle member.
 10. A compressed-gas electrical circuit breaker as in claim 9 further comprising several spring-loaded laminations within a tube disposed around the movable contact and supporting the blast piston.
 11. A compressed-gas electrical circuit breaker as in claim 10 in which the nozzle member is of concave shape at its end facing the stationary contact. 